Plasma treatment for semiconductor devices

ABSTRACT

A semiconductor device having a polymer layer and a method of fabricating the same is provided. A two-step plasma treatment for a surface of the polymer layer includes a first plasma process to roughen the surface of the polymer layer and loosen contaminants, and a second plasma process to make the polymer layer smoother or make the polymer layer less rough. An etch process may be used between the first plasma process and the second plasma process to remove the contaminants loosened by the first plasma process. In an embodiment, the polymer layer exhibits a surface roughness between about 1% and about 8% as measured by Atomic Force Microscopy (AFM) with the index of surface area difference percentage (SADP) and/or has surface contaminants of less than about 1% of Ti, less than about 1% of F, less than about 1.5% Sn, and less than about 0.4% of Pb.

TECHNICAL FIELD

This disclosure relates generally to semiconductor devices and, moreparticularly, to plasma-treated surfaces for semiconductor devices toreduce or prevent contaminants.

BACKGROUND

Since the invention of the integrated circuit (IC), the semiconductorindustry has experienced continued rapid growth due to continuousimprovements in the integration density of various electronic components(e.g., transistors, diodes, resistors, capacitors, etc.). For the mostpart, this improvement in integration density has come from repeatedreductions in minimum feature size, which allows more components to beintegrated into a given area.

The past few decades have also seen many shifts in semiconductorpackaging that have impacted the entire semiconductor industry. Theintroduction of surface-mount technology (SMT) and ball grid array (BGA)packages were generally important steps for high-throughput assembly ofa wide variety of IC devices, while at the same time allowing forreduction of the pad pitch on the printed circuit board. Conventionallypackaged ICs have a structure basically interconnected by fine gold wirebetween metal pads on the die and electrodes spreading out of moldedresin packages. On the other hand, some CSP or BGA packages rely onbumps of solder to provide an electrical connection between contacts onthe die and contacts on a substrate, such as a packaging substrate, aprinted circuit board (PCB), another die/wafer, or the like. Other CSPor BGA packages utilize a solder ball or bump placed onto a conductivepillar, relying on the soldered joint for structural integrity. In thesesituations, it is typical to cover the substrate around the solder ballsor bumps with a polymer material to protect the surface of thesubstrate. An underfill material is also typically placed between the ICand the underlying substrate, e.g., packaging substrate, to providemechanical strength and to protect the IC from environmentalcontaminants.

In some devices, the polymer surface was purposefully roughened, therebycreating a coral-like surface. This roughened surface was believed tocreate a stronger bond between the polymer material and the underfillmaterial, reducing delamination between the underfill material and thepolymer surface. It has been found, however, that this roughened surfacealso induces additional contaminants during processing. For example, theroughened surface appears to increase the amount of tape residue fromapplying tape during a backside thinning process.

SUMMARY

A two-step plasma treatment process for providing a polymer layer havinga surface with fewer contaminants and less roughness is provided. Afterperforming an etch process to form an under-bump metallization (UBM)structure over the polymer layer, a first plasma treatment process isperformed. The first plasma treatment process roughens the surface ofthe polymer layer and loosens contaminants. An etch process may beperformed to remove the loosened contaminants. A second plasma treatmentprocess is then performed to make the polymer surface smoother, or makethe surface of the polymer layer less rough. In an embodiment, thepolymer layer exhibits a surface roughness between about 1% and about 8%as measured by surface area difference percentage (SADP) and/or hassurface contaminants of less than about 1% of Ti, less than about 1% ofF, about less than 1.5% Sn, and/or less than about 0.4% of Pb.

Other embodiments are disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIGS. 1-7 illustrate various intermediate stages of a method of forminga semiconductor device in accordance with an embodiment;

FIG. 8 includes photographs of surfaces fabricated using a single-stepplasma process and a two-step plasma process;

FIG. 9 is a graph comparing the surface roughness of samples fabricatedusing a single-step plasma process and a two-step plasma process; and

FIG. 10 are tables comparing the contaminants found in samples using asingle-step plasma process and a two-step plasma process.

DETAILED DESCRIPTION

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative of specific ways to make and use theembodiments, and do not limit the scope of the disclosure.

Embodiments described herein relate to the use of a two-step plasmatreatment for polymer surfaces that provide a surface free ofcontaminants for use with semiconductor devices. As will be discussedbelow, embodiments are disclosed that utilize a first plasma treatmentprocess to first remove contaminants from a surface of a substrate and asecond plasma treatment process to make the surface smoother, whereinthe substrate may be a die, wafer, printed circuit board, packagingsubstrate, or the like. It is believed that the process described hereinallow for a substantially contaminant free surface as well as providinga smoother surface upon which further contamination from, for example, ataping process is reduced and/or prevented. Throughout the various viewsand illustrative embodiments, like reference numerals are used todesignate like elements.

FIGS. 1-7 illustrate various intermediate stages of a method of forminga semiconductor device in accordance with an embodiment. Referring firstto FIG. 1, a portion of a substrate 102 having optional electricalcircuitry 104 formed thereon is shown in accordance with an embodiment.The substrate 102 may comprise, for example, bulk silicon, doped orundoped, or an active layer of a semiconductor-on-insulator (SOI)substrate. Generally, an SOI substrate comprises a layer of asemiconductor material, such as silicon, formed on an insulator layer.The insulator layer may be, for example, a buried oxide (BOX) layer or asilicon oxide layer. The insulator layer is provided on a substrate,typically a silicon or glass substrate. Other substrates, such as amulti-layered or gradient substrate may also be used.

The optional electrical circuitry 104 formed on the substrate 102 may beany type of electrical circuitry suitable for a particular application.In an embodiment, the electrical circuitry 104 includes electricaldevices formed on the substrate 102 with one or more dielectric layersoverlying the electrical devices. Metal layers may be formed betweendielectric layers to route electrical signals between the electricaldevices. Electrical devices may also be formed in one or more dielectriclayers.

For example, the electrical circuitry 104 may include various N-typemetal-oxide semiconductor (NMOS) and/or P-type metal-oxide semiconductor(PMOS) devices, such as transistors, capacitors, resistors, diodes,photo-diodes, fuses, and the like, interconnected to perform one or morefunctions. The functions may include memory structures, processingstructures, sensors, amplifiers, power distribution, input/outputcircuitry, or the like. One of ordinary skill in the art will appreciatethat the above examples are provided for illustrative purposes only tofurther explain applications of some illustrative embodiments and arenot meant to limit the disclosure in any manner. Other circuitry may beused as appropriate for a given application.

Also shown in FIG. 1 is an inter-layer dielectric (ILD) layer 108. TheILD layer 108 may be formed, for example, of a low-K dielectricmaterial, such as phosphosilicate glass (PSG), borophosphosilicate glass(BPSG), fluorinated silicate glass (FSG), SiO_(x)C_(y), Spin-On-Glass,Spin-On-Polymers, silicon carbon material, compounds thereof, compositesthereof, combinations thereof, or the like, by any suitable method knownin the art, such as spinning, chemical vapor deposition (CVD), andplasma-enhanced CVD (PECVD). It should also be noted that the ILD layer108 may comprise a plurality of dielectric layers.

Contacts, such as contacts 110, are formed through the ILD layer 108 toprovide an electrical contact to the electrical circuitry 104. Thecontacts 110 may be formed, for example, by using photolithographytechniques to deposit and pattern a photoresist material on the ILDlayer 108 to expose portions of the ILD layer 108 that are to become thecontacts 110. An etch process, such as an anisotropic dry etch process,may be used to create openings in the ILD layer 108. The openings may belined with a diffusion barrier layer and/or an adhesion layer (notshown), and filled with a conductive material. In an embodiment, thediffusion barrier layer comprises one or more layers of TaN, Ta, TiN,Ti, CoW, or the like, and the conductive material comprises copper,tungsten, aluminum, silver, and combinations thereof, or the like,thereby forming the contacts 110 as illustrated in FIG. 1.

One or more inter-metal dielectric (IMD) layers 112 and the associatedmetallization layers (not shown) are formed over the ILD layer 108.Generally, the one or more IMD layers 112 and the associatedmetallization layers are used to interconnect the electrical circuitry104 to each other and to provide an external electrical connection. TheIMD layers 112 may be formed of a low-K dielectric material, such as FSGformed by PECVD techniques or high-density plasma CVD (HDPCVD), or thelike, and may include intermediate etch stop layers. Contacts 114 areprovided in the uppermost IMD layer to provide external electricalconnections.

It should be noted that one or more etch stop layers (not shown) may bepositioned between adjacent ones of the dielectric layers, e.g., the ILDlayer 108 and the IMD layers 112. Generally, the etch stop layersprovide a mechanism to stop an etching process when forming vias and/orcontacts. The etch stop layers are formed of a dielectric materialhaving a different etch selectivity from adjacent layers, e.g., theunderlying semiconductor substrate 102, the overlying ILD layer 108, andthe overlying IMD layers 112. In an embodiment, etch stop layers may beformed of SiN, SiCN, SiCO, CN, combinations thereof, or the like,deposited by CVD or PECVD techniques.

A protective layer 116 may be formed of a dielectric material, such asSiN, a plasma-enhance oxide (PEOX), a plasma-enhanced SiN (PE-SiN),undoped silicate glass (USG), plasma-enhanced USG (PE-USG), or the like,and patterned over the surface of the uppermost IMD layer 112 to providean opening over the contacts 114 and to protect the underlying layersfrom various environmental contaminants. Thereafter, conductive pads 118are formed and patterned over the protective layer 116. The conductivepads 118 provide an electrical connection upon which a UBM structure,such as a copper pillar structure, may be formed for externalconnections. The conductive pads 118 may be formed of any suitableconductive materials, such as copper, tungsten, aluminum, silver,combinations thereof, or the like.

One or more passivation layers, such as a first passivation layer 120,are formed and patterned over the conductive pads 118 as illustrated inFIG. 1. The first passivation layer 120 may be formed of a dielectricmaterial, such as SiN, USG, PE-USG, PE-SiN, combinations thereof, and/orthe like, by any suitable method, such as CVD, physical vapor deposition(PVD), or the like. In an embodiment, the passivation layer 120comprises a multi-layer structure of SiN and PE-USG.

One of ordinary skill in the art will appreciate that a single layer ofconductive pads and a passivation layer are shown for illustrativepurposes only. As such, other embodiments may include any number ofconductive layers and/or passivation layers. Furthermore, it should beappreciated that one or more of the conductive layers may act as aredistribution layer (RDL) to provide the desired pin or ball/bumplayout.

Any suitable process may be used to form the structures discussed aboveand will not be discussed in greater detail herein. As one of ordinaryskill in the art will realize, the above description provides a generaldescription of the features of an embodiment and that numerous otherfeatures may be present. For example, other circuitry, liners, barrierlayers, under-bump metallization configurations, and the like, may bepresent. The above description is meant only to provide a context forembodiments discussed herein and is not meant to limit the disclosure orthe scope of any claims to those specific embodiments.

It should be noted that the substrate 102 in the embodiment discussedabove is an embodiment in which the substrate 102 is a portion of anintegrated circuit die. In other embodiments, the substrate 102 may bean interposer (with or without active and/or passive electrical elementsformed thereon), a packaging substrate, a laminate substrate, ahigh-density interconnect, or the like. These other embodiments may ormay not have the various layers described above and may have additionallayers.

FIG. 2 illustrates a second passivation layer 210 formed over the firstpassivation layer 120 and patterned to expose at least a portion of theconductive pads 118. The second passivation layer 210 may be, forexample, a polymer (e.g., polyimide, polybenzoxasole, or the like)formed by any suitable process, such as a lithography coater process, orthe like.

FIG. 3 illustrates an under bump metallization (UBM) seed layer 310deposited over the surface of the second passivation layer 210. The UBMseed layer 310 is a thin layer of a conductive material that aids in theformation of a thicker layer during subsequent processing steps. In anembodiment, the UBM seed layer 310 may be formed by depositing one ormore thin conductive layer, such as a thin layer of Cu, Ti, Ta, TiN,TaN, combinations thereof, or the like, using CVD or PVD techniques. Forexample, in an embodiment, a layer of Ti is deposited by a PVD processto form a barrier film and a layer of Cu is deposited by a PVD processover the layer of Ti. The layer of Ti helps prevent or reduce thediffusion of Cu into the underlying layers. Other materials,thicknesses, and processes may be used.

Thereafter, as illustrated in FIG. 3, a patterned mask 312 is formed andpatterned over the UBM seed layer 310 in accordance with an embodiment.The patterned mask 312 defines the lateral boundaries of the conductivepillar to be subsequently formed as discussed in greater detail below.The patterned mask 312 may be a patterned photoresist mask, hard mask, acombination thereof, or the like.

FIG. 4 illustrates the formation of a conductive pillar 410 inaccordance with an embodiment. The conductive pillar 410 may be formedof any suitable conductive material, including Cu, Ni, Pt, Al,combinations thereof, or the like, and may be formed through any numberof suitable techniques, including PVD, CVD, electrochemical deposition(ECD), molecular beam epitaxy (MBE), atomic layer deposition (ALD),electroplating, and the like. It should be noted that in someembodiments, such as those that deposit a conformal layer over theentire surface of the wafer (e.g., PVD and CVD), it may be desirable toperform an etching or planarization process (e.g., a chemical mechanicalpolishing (CMP)) to remove excess conductive material from the surfaceof the patterned mask 312.

It should also be noted that the conductive pillar 410 is illustrated asa thin layer for illustrative purposes only. In other embodiments, theconductive pillar 410 may be considerably thicker, such as having athickness between about 20 μm and about 50 μm. The conductive pillar 410may be any thickness sufficient for a desired application. Theconductive pillar 410 may also have various shapes.

FIG. 4 also illustrates formation of an optional conductive cap layer412 formed over the conductive pillar 410. As described in greaterdetail below, solder material is formed over the conductive pillar 410.During the soldering process, an inter-metallic compound (IMC) layer(not shown) may be naturally formed at the joint between the soldermaterial and the underlying surface. It has been found that somematerials may create a stronger, more durable IMC layer than others. Assuch, it may be desirable to form a cap layer, such as the conductivecap layer 412, to provide an IMC layer having more desirablecharacteristics. For example, in an embodiment in which the conductivepillar 410 is formed of copper, a conductive cap layer 412 formed ofnickel may be desirable. Other materials, such as Pt, Au, Ag,combinations thereof, or the like, may also be used. The conductive caplayer 412 may be formed through any number of suitable techniques,including PVD, CVD, ECD, MBE, ALD, electroplating, and the like.

Furthermore, FIG. 4 also illustrates formation of solder material 414.In an embodiment, the solder material 414 comprises SnPb, a high-Pbmaterial (e.g., Pb₉₅Sn₅), a Sn-based solder, a lead-free solder,eutectic solder, or other suitable conductive material.

Thereafter, as illustrated in FIG. 5, the patterned mask 312 (see FIG.4) may be removed. In embodiments in which the patterned mask 312 isformed from photoresist materials, the photoresist may be stripped by,for example, a chemical solution such as a mixture of ethyl lactate,anisole, methyl butyl acetate, amyl acetate, cresol novolak resin, anddiazo photoactive compound (referred to as SPR9), or another strippingprocess. A first UMB etch process may be performed to remove exposedportions of the UBM seed layer 310 from the surface of the secondpassivation layer 210. In an embodiment in which the UBM seed layer 310comprises a Ti layer and a Cu layer, a wet dip in a chemical solution ofphosphoric acid (H₃PO₄) and hydrogen peroxide (H₂O₂), referred to asDPP, with 1% hydrofluoric (HF) acid, or another cleaning process, may beused.

As illustrated in FIG. 5, contaminants 516 may remain on the surface ofthe second passivation layer 210, even after the cleaning processdescribed above. To remove these contaminants, one or more plasmatreatments are performed. In an embodiment, a first plasma treatment isperformed to slightly roughen the surface of the second passivationlayer 210, thereby loosening the contaminants 516. A second plasmatreatment is performed subsequently to reduce the roughness, but notcompletely, of the second passivation layer 210.

In an embodiment, the first plasma treatment comprises a N₂ plasmatreatment using an N₂ flow rate of about 100 sccm to about 1000 sccm ata pressure of about 16 Pa to about 100 Pa with a microwave power ofabout 500 Watts to about 2000 Watts and an RF power of about 250 Wattsto about 500 Watts. This N₂ plasma treatment may be performed for about10 seconds to about 90 seconds to sufficiently roughen the secondpassivation layer 210 and loosen the contaminants 516.

In another embodiment, the first plasma treatment comprises a CF₄/O₂plasma treatment using a CF₄ flow rate of about 50 sccm to about 200sccm and an O₂ flow rate of about 50 sccm to about 200 sccm at apressure of about 16 Pa to about 100 Pa with a microwave power of about500 Watts to about 2000 Watts and an RF power of about 100 Watts toabout 400 Watts. This CF₄/O₂ plasma treatment may be performed for about10 seconds to about 90 seconds to sufficiently roughen the secondpassivation layer 210 and loosen the contaminants 516.

Thereafter, a second UBM etch process may be performed. After thecontaminants have been loosened by the first plasma treatment, thesecond UBM etch process may be used to remove the loosened contaminants.In an embodiment in which the UBM seed layer 310 comprises a Ti layerand a Cu layer, the second UBM etch process may comprise a wet dip a 1%HF acid, or another cleaning process, may be used. It is believed thatwhen the UBM seed layer 310 comprises a Ti layer and a Cu layer, thecontaminants 516 are mostly Ti contaminants. As such, the wet dip in 1%HF acid is designed to mainly etch the Ti contaminants. If othercontaminants are found, then other etchants may be used as well, such asthe DPP solution to remove Cu contaminants.

FIG. 6 illustrates the surface roughness of the second passivation layer210 and the removal of the contaminants 516 (see FIG. 5) after the firstplasma treatment and the second UBM etch process. An O₂ plasma treatmentmay also be performed at this stage to remove any by-products that mayhave formed as a result of a reaction between the plasma treatment andthe material (e.g., polymer) of the protective layer 210. FIG. 6 alsoillustrates a solder reflow process.

FIG. 7 illustrates a second plasma treatment in accordance with anembodiment. As discussed above, it has been found that applying a tapeor other adhesive for subsequent processing, such as backside thinning,to a rough surface, such as that used in other systems, often results intape residue remaining on the rough surface of the protective layer 210,possibly causing delamination between the second passivation layer 210and an underfill material. The tape residue on the solder material 414may also cause a cold joint. In these situations, it may be desirable toperform a second plasma treatment to make the surface of the secondpassivation layer 210 smoother or to make the surface of the secondpassivation layer 210 less rough. This smoother surface is less likelyto cause tape residue.

In an embodiment, the second plasma treatment comprises a N₂ plasmatreatment using an N₂ flow rate of about 100 sccm to about 1000 sccm ata pressure of about 16 Pa to about 100 Pa with a microwave power ofabout 500 Watts to about 2000 Watts and an RF power of about 50 Watts toabout 250 Watts. This N₂ plasma treatment may be performed for about 10seconds to about 90 seconds.

In another embodiment, the second plasma treatment comprises an Ar/O₂plasma treatment using a Ar flow rate of about 50 sccm to about 200 sccmand an O₂ flow rate of about 50 sccm to about 200 sccm at a pressure ofabout 16 Pa to about 100 Pa with a microwave power of about 0 Watts toabout 1000 Watts and an RF power of about 50 Watts to about 250 Watts.This Ar₂/O₂ plasma treatment may be performed for about 10 seconds toabout 90 seconds.

FIG. 8 illustrates results that may be obtained by embodiments such asthose discussed herein. FIGS. 8A-1 through 8D-1 illustrate imagesobtained by 100K Scanning Electron Microscope (SEM) of a polymer surfaceafter being subjected to a two-step plasma process such as thatdescribed above. The surface roughness of FIGS. 8A-1 through 8D-1 weremeasured to have a surface roughness of 2.84%, 2.92%, 2.2%, and 3.9%,respectively, as measured by Atomic Force Microscopy (AFM) with theindex of the surface area difference percentage (SADP). Generally, SADPis an equation that may be used to measure the roughness of athree-dimensional surface that is calculated by dividing the differencebetween the three-dimensional area and the two-dimensional area by thetwo-dimensional area, and multiplying the result by 100, or in otherwords, (((3D area−2D area)/2D area)*100).

In comparison, FIGS. 8A-2 through 8D-2 illustrate images obtained by100K SEM of a polymer surface after performing a single rougheningplasma treatment. The surface roughness of these surfaces were measuredas 13.9%, 22.5%, 12.3%, and 9.41%, respectively, as measured by theSAPD.

FIG. 9 illustrates the difference in surface roughness of the secondpassivation layer 210 after a two-step plasma process as compared to asingle-step plasma process. In particular, the samples to the left ofthe dotted line 900 represent the surface roughness of the secondpassivation layer 210 after using a two-step process such as thosediscussed above. The samples to the right of the dotted line 900represent the surface roughness of a protective layer seen previoussystems using a single plasma process. As illustrated in FIG. 9, thetwo-step plasma process results in a surface roughness of about 1% toabout 8%, while the one-step plasma process resulted in a surfaceroughness of greater than 8%.

FIG. 10 illustrates two tables identifying the composition of thesurface of the second passivation layer 210 using a two-step plasmatreatment and a single-step plasma treatment. Table 1004 illustrates theamounts of Ti, F, Sn, and Pb that were found on the surface of aprotective layer after a single-step plasma treatment, and table 1002illustrates the amounts of those elements after a two-step plasmatreatment, as measured by an X-ray Photoelectron Spectroscopy (XPS). Ascan be seen in FIG. 10, the two-step plasma process significantlyreduces the amount of all of these elements.

It is believed that two-step plasma process results in a surfaceroughness such that the UBM seed layer residue is effectively removed,but yet obtains a surface roughness that reduces or prevents adhesivecontaminants from, for example, tape.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. In addition, each claim constitutes a separateembodiment, and the combination of various claims and embodiments arewithin the scope of the disclosure.

What is claimed is:
 1. A method of forming a device, the methodcomprising: providing a substrate; forming a contact pad on thesubstrate; forming a protective layer over the contact pad such that atleast a portion of the contact pad is exposed; forming an under bumpmetallization (UBM) structure in electrical contact with the contactpad; forming a conductive bump on the UBM structure; after forming theunder bump metallization, performing a first plasma process on exposedsurfaces of the protective layer, the first plasma process roughening asurface of the protective layer; performing one or more process stepsafter the performing the first plasma process; and performing a secondplasma process on exposed surfaces of the protective layer, the secondplasma process removing portions of the protective layer and reducingthe roughness of the protective layer.
 2. The method of claim 1, whereinthe protective layer is polyimide.
 3. The method of claim 1, wherein theprotective layer is polybenzoxasole.
 4. The method of claim 1, whereinthe UBM structure includes a titanium layer and an overlying copperlayer.
 5. The method of claim 1, wherein the one or more process stepsincludes an etch process to remove contaminants loosened by the firstplasma process.
 6. The method of claim 1, wherein the first plasmaprocess comprises an N₂ plasma treatment.
 7. The method of claim 1,wherein the first plasma process comprises a CF₄/O₂ plasma treatment. 8.The method of claim 1, wherein the second plasma process comprises a N₂plasma treatment.
 9. The method of claim 1, wherein the second plasmaprocess comprises an Ar/O₂ plasma treatment.
 10. A method of forming adevice, the method comprising: providing a substrate having a protectivelayer formed thereon and an under bump metallization (UBM) structureformed through the protective layer; after the providing the substratehaving the UBM structure, performing a first plasma process on exposedsurfaces of the protective layer, the first plasma process roughening asurface of the protective layer; removing contaminants from a surface ofthe protective layer after the performing the first plasma process; andperforming a second plasma process on exposed surfaces of the protectivelayer, the second plasma process removing portions of the protectivelayer and reducing the roughness of the protective layer.
 11. The methodof claim 10, wherein the protective layer is polyimide.
 12. The methodof claim 10, wherein the protective layer is polybenzoxasole.
 13. Themethod of claim 10, wherein the UBM structure includes a titanium layerand an overlying copper layer.
 14. The method of claim 10, wherein thefirst plasma process comprises an N₂ plasma treatment.
 15. The method ofclaim 10, wherein the first plasma process comprises a CF₄/O₂ plasmatreatment.
 16. The method of claim 10, wherein the second plasma processcomprises a N₂ plasma treatment.
 17. The method of claim 10, wherein thesecond plasma process comprises an Ar/O₂ plasma treatment.